The present invention relates to EGR valves and in particular EGR valves including a force balanced diaphragm-piston assembly and outwardly opening valve closure element to permit cleaning of same.
Exhaust gas recirculation (EGR) valves form an integral part of the exhaust gas purification system of internal combustion engines. The EGR valve is utilized to recirculate a predetermined amount of the exhaust gas back to the intake manifold of the engine. The amount of exhaust gas permitted to flow back to the intake manifold is usually controlled in an open loop fashion by controlling the flow area of the valve. Such open loop control makes it difficult to accurately control the percentage of exhaust gas flow over the useful life of the valve as the various components of the valve wear, or due to the variability of the vacuum signals communicated to such valves. To overcome the lack of consistently available vacuum to control a moveable diaphragm, electrically actuated solenoids have been used to replace the totally vacuum actuated diaphragm. Further, EGR valves typically utilized an inward opening valve closure element which is moved into its protective housing relative to a cooperating valve seat. Over the useful life of such valves carbon accumulates on the valve closure element and upon its valve seat thereby preventing the valve from completing closing. Such valve closure elements are positioned within the housing or body of the EGR valve and make it impossible to clean the valve closure element and the valve seat thereby necessitating replacement of this integral pollution system component.
It is therefore an object of the present invention to provide an EGR valve which is devoid of the deficiencies of the prior art. A further object of the present invention is to provide an exhaust gas recirculation valve which is capable of having its valve seat and closure element cleaned thereby permitting the valve to be reinstalled.
A further object of the present invention is to provide an EGR valve having position feedback capability thereby permitting the accurate control of the percent of exhaust gas permitted to flow into the intake manifold of the engine.
An additional object of the present invention is to provide an EGR valve having a forced balanced diaphragm-piston assembly thereby permitting solenoid activation thereof utilizing a minimum activation force thereby yielding a rapidly responding, actuately positionable valve.
Accordingly, the invention comprises an EGR valve for an engine comprising means for mounting the valve to an engine, including an inlet adapted to receive exhaust gas, and an outlet adapted to receive engine vacuum and adapted to communicated the received exhaust gas to the intake of the engine and a valve seat positioned about the inlet on an exterior surface thereof. The valve including housing means supported by the mounting means including an atmospheric chamber and a vacuum chamber. The housing means including means for communicating vacuum to the vacuum chamber and a pressure balanced diaphragm-piston assembly supported by the housing means for dividing the housing means into the atmospheric and vacuum chambers. The assembly comprises: a plate supported at its outer periphery by the housing means, the plate including an opening substantially aligned with said inlet, and a flexible diaphragm having an outer portion supported by the plate about said opening, and a flexible inner portion defining an annular opening. The assembly further includes piston means comprising an upper element adapted to receive the inner portion of the diaphragm, a rod extending from the upper element through the inlet and an outward opening valve closure element for seating upon the valve seat. The valve further includes a solenoid assembly responsive to control signals input thereto comprising a movable armature and a rod extending therefrom for engaging the upper element and for moving the piston means outwardly off from said valve seat; biasing means supported within the housing means for urging the piston means into the housing and upon the valve seat; and means for sensing the position of the piston means.
Many other objects, features, advantages and purposes of the invention will be clear from the detailed description of the drawings.